Introduction: Cerebral microbleeds are more common in chronic kidney disease (CKD) and dialysis patients compared to the general population. Diminished kidney function alone appears to be a risk factor for microbleeds, independent of age and hypertension. Microbleed burden in CKD patients is associated with increased risk of future hemorrhagic stroke and with cognitive dysfunction. The mechanisms that drive uremic microbleed formation are unclear.
Hypothesis: We hypothesized that CKD mice are predisposed to develop cerebral microhemorrhages (the pathologic substrate of microbleeds), and that a standardized inflammatory stimulus (lipopolysaccharide, LPS) will amplify microhemorrhage burden in CKD mice compared to non-CKD controls (CTL). We also hypothesized that uremia induces depletion of tight junction proteins, altering blood-brain barrier integrity and representing a potential mechanism of microbleed formation.
Methods: Animal groups included CTL (n=3), CKD (n=3), CTL+LPS (n=5) and CKD+LPS (n=5). CKD induction in male C57BL/6 mice was achieved via nephrotoxic adenine diet x18 days. Two weeks following CKD induction, CKD and control mice were treated with LPS 1 mg/kg i.p. dosed at 0, 6 and 24 hours. Brains were harvested one week after LPS injections and 40-micron sections were stained using Prussian blue to identify microhemorrhages. Immunohistochemistry was performed for the blood-brain barrier tight junction protein claudin-5.
Results: CKD mice had significantly elevated blood urea nitrogen, and tubulointerstitial fibrosis was present on kidney histology. Total number of microhemorrhages per brain was 2.3±1.5 (mean ± standard error of the mean) for CTL mice, 8.3±1.5 for CKD mice, 23.2±4.2 for CTL+LPS mice, and 27.6±6.2 for CKD+LPS mice (p<0.05 for CKD+LPS vs. CTL). Immunostaining showed decreased claudin-5 expression in CKD mice compared to CTL.
Conclusions: We have generated a mouse model that will facilitate future mechanistic studies in the field of uremic microbleeds. Our initial findings suggest that CKD alters blood-brain barrier integrity and that inflammation amplifies development of microbleeds in CKD.